1. Field of the Invention
The present invention relates to certain novel thermoplastic elastomers and methods for their preparation.
2. Description of the Prior Art
Copolymer systems that are well separated can display elasticity without the requirement of crosslinking provided that one of the phases, often called the hard phase, is capable of a thermally reversible change of state. Such copolymers are known as thermoplastic elastomers and a large number of them exist [Legge et al., Eds., Thermoplastic Elastomers, A Comprehensive Review, N.Y., (1987)]. Examples of thermoplastic elastomers include: poly(styrene-dienestyrene)s and their blends [Porter et al., U.S. Pat. No. 3,149,182 (1964); Legge et al., "Chemistry and Technology of Block Copolymers" in Applied Polymer Science, Craver and Tess, Eds., ACS, Washington, D.C., p. 394 (1975)]; polyolefins and their blends [Caran et al., Rubber Chem. & Tech., Vol. 56, p. 1045 (1983); Coran et al., Rubber Chem. & Tech., Vol. 56, p. 210 (1983); poly- (urethane-ether)s [Oertel, Ed., Polyurethane Handbook, Carl Hanser Verlag, Munich (1985); poly(amide) copolymers [Nelb et al., "Polyesteramides and polyetheresteramides: Thermoplastic polyamide Elastomers": in Thermoplastic Elastomers, A Comprehensive Review, Eds., Legge et al., N.Y. (1987)]; poly(ester) copolymers including those containing poly(pivalolactone) [Wolfe, "Elastomeric Poly(ester-ether) Block Copolymers" in Block Copolymers: Science and Technology, Eds. Meier, Harwood Academic, N.Y. (1983) 145]; ionomeric systems [Agarwal, U.S. Pat. No. 4,371,652 (1983); Lundberg et al., U.S. Pat. No. 4,481,318 (1984)]; acrylics [Falk et al., U.S. Pat. No. 4,473,679 (1984)], and poly(siloxane) copolymers. Several poly(siloxane) copolymers have been reported in the literature [Nyilas, U.S. Pat. No. 3,562,352 (1971); Riffle et al., J. Macromol. Sci., Chem., A15, p. 967 (1981); Gaylord, U.S. Pat. No. 4,120,570 (1978); Saam et al., Ind. Eng. Chem. Prod. Res., Vol. 10, p. 10 (1971); Kania et al., J. Appli. Polym. Sci., Vol. 27, p. 139 (1982)]; and have the advantage that they can be used as elastomers at very low temperatures.
Reported copolysiloxanes include: poly-(siloxane)-poly(urethane)s; poly(siloxane)-poly (carbonate)s; poly(siloxane)-poly(methacrylate)s; poly(siloxane)-poly(amide)s; poly(siloxane)-methylstyrene block copolymers, and poly(siloxane)-polypeptide block copolymers.
In many practical applications the crystalline or semi-crystalline state in polymeric systems is highly preferred for thermally induced changes in state; however, very few of the known polysiloxane copolymers exhibit a crystalline or semi-crystalline phase. The crystalline state also enhances physical properties such as solvent resistance and ultimate strength.
It is an object of the present invention to provide novel semi-crystalline, thermoplastic siloxane elastomers.
It is a further object of the present invention to provide novel methods for preparing such elastomers.